U.S. patent application number 13/510510 was filed with the patent office on 2012-09-13 for lighting device, method and light wavelength conversion wheel assembly for color tuning thereof.
This patent application is currently assigned to APPOTRONICS CORPORATION LIMITED. Invention is credited to Yanzheng Xu.
Application Number | 20120230013 13/510510 |
Document ID | / |
Family ID | 44031113 |
Filed Date | 2012-09-13 |
United States Patent
Application |
20120230013 |
Kind Code |
A1 |
Xu; Yanzheng |
September 13, 2012 |
LIGHTING DEVICE, METHOD AND LIGHT WAVELENGTH CONVERSION WHEEL
ASSEMBLY FOR COLOR TUNING THEREOF
Abstract
A lighting device, a method and a light wavelength conversion
wheel assembly (4) for color tuning thereof. The lighting device
includes a light source. The light source includes an excitation
light source (1) and a movement unit. The movement unit includes a
light wavelength conversion wheel assembly (4) having a heat
dissipation base (40). The heat dissipation base (40) is divided
into a number of areas (41) carrying different excited materials
(46), and is controlled to rotate intermittently or rotate to a
predetermined angle around a wheel shaft serving as a center. The
heat dissipation base (40) faces the exciting light and is
illuminated locally, and the illumination area is not larger than
any of the areas (41) carrying the excited materials (46). A
control unit controls the rotation so that a predetermined area is
rotated into the illumination area of the exciting light. Output
light of a predetermined color is provided by the excitation light
source (1) and the predetermined area or the excited material (46)
located in the predetermined area. A pattern having high brightness
or high saturation as well as a higher combined efficiency of white
light is provided, and the cost is low.
Inventors: |
Xu; Yanzheng; (Shenzhen,
CN) |
Assignee: |
APPOTRONICS CORPORATION
LIMITED
Guangdong
CN
|
Family ID: |
44031113 |
Appl. No.: |
13/510510 |
Filed: |
November 19, 2010 |
PCT Filed: |
November 19, 2010 |
PCT NO: |
PCT/CN10/01856 |
371 Date: |
May 17, 2012 |
Current U.S.
Class: |
362/84 ;
362/317 |
Current CPC
Class: |
F21W 2131/406 20130101;
G02B 26/008 20130101; G02B 27/1053 20130101; G02B 27/149 20130101;
G02B 7/006 20130101; G03B 21/204 20130101 |
Class at
Publication: |
362/84 ;
362/317 |
International
Class: |
F21V 13/02 20060101
F21V013/02; F21V 29/00 20060101 F21V029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2009 |
CN |
200910189519.8 |
Claims
1. A wavelength conversion wheel assembly, comprising: a heat
dissipating base having a plurality of segments, at least two
segments each carrying a wavelength conversion material, the at
least two segments being spatially separated and not contacting
each other; a mounting device for supporting the heat dissipating
base to rotate around a rotation axis, wherein the heat dissipating
base is controlled to rotate intermittently or to predetermined
angles.
2. The wavelength conversion wheel assembly of claim 1, wherein the
plurality of segments have substantially identical sizes, have a
circular shape, and are distributed in a circular manner on the
heat dissipating base.
3. The wavelength conversion wheel assembly of claim 1, wherein the
heat dissipating base has a plate shape or a cylindrical shape.
4. The wavelength conversion wheel assembly of claim 1, wherein the
wavelength conversion materials include phosphor, dye or quantum
dots.
5. The wavelength conversion wheel assembly of claim 1, wherein the
wavelength conversion materials are coated on the heat dissipating
base, filled into the heat dissipating base, or adhered to the heat
dissipating base.
6. The wavelength conversion wheel assembly of claim 1, wherein the
heat dissipating base is made of a transparent material.
7. The wavelength conversion wheel assembly of claim 6, wherein the
heat dissipating base includes two heat conductive glass plates
clamped together, and wherein the wavelength conversion materials
are sandwiched between the two heat conductive glass plates.
8. The wavelength conversion wheel assembly of claim 1, wherein at
least one of segments of the heat dissipating base further includes
a filter.
9. The wavelength conversion wheel assembly of claim 1, further
comprising: a gear disposed on a rotating shaft of the heat
dissipating base or at an edge of the heat dissipating base.
10. The wavelength conversion wheel assembly of claim 1, wherein
the heat dissipating base includes a heat dissipating plate having
a plurality of through holes, wherein each segment is disposed in a
through hole, each segment including a transparent heat conducting
plate disposed in the through holes for carrying the wavelength
conversion material.
11. A lighting device, comprising: a light source; a light output
port; a light guiding device for guiding the light from the light
source to the light output port; wherein the light source includes:
an excitation light source for providing an excitation light; and a
moving unit, wherein the moving unit includes a wavelength
conversion wheel assembly which includes: a heat dissipating base
having a plurality of segments, at least two segments each carrying
a wavelength conversion material, the at least two segments being
spatially separated and not contacting each other, and a mounting
device for supporting the heat dissipating base to rotate around a
rotation axis, wherein the heat dissipating base is controlled to
rotate intermittently or to predetermined angles, wherein the heat
dissipating base faces the excitation light and is partially
illuminated by the excitation light, wherein an area of
illumination is no greater than an area of any one of the segments;
and a control unit for controlling a movement of the wavelength
conversion wheel assembly so that a selected one of the plurality
of segments of the heat dissipating base is illuminated by the
excitation light to generate an output light.
12. The lighting device of claim 11, wherein the excitation light
source includes an array of a plurality of light emitting diodes
(LED), and wherein the lighting device further comprises an array
of a plurality of collimating lenses, each collimating lens being
aligned with an LED to collimate a light emitted by the LED into
near parallel light.
13. The lighting device of claim 11, wherein the light guiding
device includes a focusing lens for focusing the light from the
light source to the light output port.
14. The lighting device of claim 11, further comprising a second
focusing lens for focusing the excitation light onto the wavelength
conversion material on the heat dissipating base.
15. The lighting device of claim 13, further comprising a second
collimating lens disposed between the heat dissipating base and the
focusing lens for collimating the light from the light source into
a near parallel light to be focused by the focusing lens.
16. The lighting device of claim 15, further comprising an integral
lens set disposed between the second collimating lens and the
focusing lens.
17. The lighting device of claim 11, further comprising: a filter
plate having a size substantially identical to a size of the
plurality of segments of the heat dissipating base; and a second
wheel carrying the filter plate; wherein the control unit controls
a movement of second wheel to move the filter plate in and out of
an optical path between the heat dissipating base and the light
guiding device.
18. The lighting device of claim 11, wherein the heat dissipating
base of the wavelength conversion wheel assembly includes at least
one segment that carries a wavelength conversion material, the heat
dissipating base further comprising a wavelength selection filter
disposed in the at least one segment on a side facing the
excitation light.
19. The lighting device of claim 11, further comprising a pattern
wheel carrying pattern plates aligned with the light output
port.
20. A color tuning method for a lighting device, wherein the
lighting device comprises a light source, a light output port, and
a light guiding device for guiding the light from the light source
to the output port, wherein the light source includes an excitation
light source for providing an excitation light, the method
comprising: providing a moving unit, wherein the moving unit
includes a wavelength conversion wheel assembly which includes: a
heat dissipating base having a plurality of segments, at least two
segments each carrying a wavelength conversion material, the at
least two segments being spatially separated and not contacting
each other, and a mounting device for supporting the heat
dissipating base to rotate around a rotation axis, wherein the heat
dissipating base is controlled to rotate intermittently or to
predetermined angles, wherein the heat dissipating base faces the
excitation light and is partially illuminated by the excitation
light, wherein an area of illumination is no greater than an area
of any one of the segments; operating a control unit to control the
wavelength conversion wheel assembly, wherein the wavelength
conversion wheel assembly moves so that a selected one of the
plurality of segments is disposed in an illumination path of the
excitation light; and generating an output light of a selected
color, wherein the color of the output light is determined by the
excitation light source and the selected segment or the wavelength
conversion material carried by the selected segment.
21. The color tuning method of claim 20, wherein the excitation
light source includes an array of a plurality of light emitting
diodes (LED) and an array of a plurality of collimating lenses,
each collimating lens being aligned with an LED to collimate a
light emitted by the LED into near parallel light.
22. The color tuning method of claim 21, wherein the LEDs are blue
LEDs.
23. The color tuning method of claim 20, wherein the heat
dissipating base is made of a transparent material or have a
plurality of through holes in which the segments are disposed, the
method further comprising: providing a filter on or near the heat
dissipating base on a side facing the light guiding device, wherein
the filter is disposed in an optical path between the heat
dissipating base and the light guiding device for selectively
transmitting light of a predetermined wavelength range or
predetermined output angle range.
24. The color tuning method of claim 20, further comprising:
forming a wavelength selection filter on the heat dissipating base
on a side facing the excitation light for reflecting the converted
light.
25. The color tuning method of claim 20, wherein the operating step
includes operating the control unit at predetermined times or
intermittently according to a predetermined color changing pattern
to select the segments.
26. The color tuning method of claim 20, further comprising: the
control unit controlling the excitation light and the moving unit
in a synchronized manner.
27. The color tuning method of claim 20, wherein the control unit
includes a stepping motor for driving the wavelength conversion
wheel assembly via gears.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to lighting devices and light
sources, and in particular, it relates to control and tuning
techniques for light sources, and tuning of the output light
color.
[0003] 2. Description of the Related Art
[0004] Currently, light sources for high power stage lighting
devices primarily use metal halide discharge lamps. Metal halide
discharge lamps are which light sources, and their life is
relatively short, from a few hundred to a few thousand hours.
Because the emission spectrum of metal halide discharge lamps is a
white continuous spectrum, output lights of different colors can
only be obtained by using color filters. The color patterns
projected by such lighting devices have relatively low color
saturation; the color is neither vivid nor rich.
[0005] To increase the color saturation of monochromatic output
light, conventional stage lighting devices sometimes use very
narrow band color filters. Although the color saturation is
increased, the brightness of the output monochromatic light is
reduced.
[0006] With the development of solid state light source
technologies, solid state light sources, in particular light
emitting diodes (LED), are becoming more widely used in state
lighting systems. But because of the limitations in heat
dissipation and light flux of LED lights, currently, LED light
sources are mainly used in low-end low power color changing light
products.
[0007] To use solid state light sources in high power stage
lighting devices, a device described in a patent application
previously filed by the same applicant (see FIG. 1) utilizes
multiple high power LED arrays to provide red (R), green (G) and
blue (B) lights separately, and utilizes light combining devices
such as an X-shaped light combiner 15 to combined the lights and
obtain output lights of desired colors.
[0008] In addition, current light source devices use a single light
source in combination with phosphor materials to generate output
light of various colors. For example, Chinese patent application
No. 2008100653661 describes a device which employs a moving unit
disposed on the optical path of a light source, the moving unit
carrying multiple phosphor materials and rotating at a high speed,
to generate an output light which is a mixture of multiple
monochromatic lights. This device can also control and adjust the
output power of the light source in real time to achieve desired
color variation of the combined output light.
[0009] A shortcoming of the above technology is that, in the
abovementioned technology by the same applicant, although the high
power stage lighting device can achieve high brightness and high
saturation monochromatic light, the color rendering capability of
the white light is still insufficient. The reason is as follows.
Conventional metal halide discharge lamps are hot light sources
whose light emitting efficiency is not affected by the output
power. For example, a 575 W lamp, whether its output flux is 49000
lumen or 110000 lumen, the light emitting efficiency is 85 lumen/W
for metal halide discharge lamps. To the contrary, the light
emitting efficiency of current high power LED decreases with
increased drive power. Moreover, in current R, G, B base color
LEDs, green LEDs have the lowest light emitting efficiency and blue
LEDs have the highest light emitting efficiency. However, because
the white spectrum contains the most green component and the least
blue component, to obtain adequate white balance, the brightness of
the white LED stage lighting device will be low. In particular, a
stage light requires a low color temperature light (e.g. 3200K) in
sometimes applications, which requires even more green light
components, resulting in even lower brightness of the white light.
Further, the above described light source uses large arrays of high
power LEDs, which increases the cost of the light source compared
to conventional devices and limits its applicability.
[0010] Although the light source device described in the above
mentioned Chinese patent application No. 2008100653661 can provide
rich color variation, it requires high rotation speed of the moving
unit to achieve desired color adjustment, which imposes high
requirement on the real time control of the light source.
SUMMARY OF THE INVENTION
[0011] To solve various problems of current technology, the present
invention is directed to a lighting device and related color tuning
methods which can be achieved with low cost. The lighting device
can provide pattern projection with relatively high efficiency of
white color light generation.
[0012] To achieve these advantages, the present invention uses a
heat dissipating moving unit which defines different segments
carrying different wavelength conversion materials; based on the
requirement for different color output light, such as required
color light for projecting onto a stage, the moving unit is moved
so that different segments are illuminated by an excitation light,
to generate output light of desired colors. This system can meet
the color requirements of state lighting and provide a low cost,
high brightness or high saturation light.
[0013] The present invention provides a wavelength conversion wheel
assembly, which includes: a heat dissipating base having a
plurality of segments, each segment carrying a wavelength
conversion material or no wavelength conversion material; and a
mounting device for supporting the heat dissipating base to rotate
around a rotation axis, wherein the heat dissipating base is
controlled to rotate intermittently or to predetermined angles.
[0014] In the above device, the plurality of segments have
substantially identical sizes, have a circular shape, and are
distributed in a circular manner on the heat dissipating base. The
heat dissipating base has a plate shape or a cylindrical shape. The
wavelength conversion materials include phosphor, dye or quantum
dots. The wavelength conversion materials are coated on the heat
dissipating base, filled into the heat dissipating base, or adhered
to the heat dissipating base.
[0015] In the above device, the heat dissipating base is made of a
transparent material. The heat dissipating base includes two heat
conductive glass plates clamped together, and the wavelength
conversion materials are sandwiched between the two heat conductive
glass plates. At least one of segments of the heat dissipating base
further includes a filter film or filter plate. The heat
dissipating base includes a heat dissipating plate having a
plurality of through holes, where each segment is disposed in a
through hole, each segment including a transparent heat conducting
plate disposed in the through holes for carrying the wavelength
conversion material. The wavelength conversion wheel assembly
further includes a gear disposed on a rotating shaft of the heat
dissipating base or at an edge of the heat dissipating base.
[0016] In another aspect, the present invention provides a lighting
device, which includes: a light source; a light output port; a
light guiding device for guiding the light from the light source to
the light output port; wherein the light source includes: an
excitation light source for providing an excitation light; and a
moving unit, wherein the moving unit includes the wavelength
conversion wheel assembly described above, wherein the heat
dissipating base faces the excitation light and is partially
illuminated by the excitation light, wherein an area of
illumination is no greater than an area of any one of the segments;
and a control unit for controlling a movement of the wavelength
conversion wheel assembly so that a selected one of the plurality
of segments of the heat dissipating base is illuminated by the
excitation light to generate an output light.
[0017] In the above device, the excitation light source includes an
array of a plurality of light emitting diodes (LED), and the
lighting device further comprises an array of a plurality of
collimating lenses, each collimating lens being aligned with an LED
to collimate a light emitted by the LED into near parallel light.
The light guiding device includes a focusing lens for focusing the
light from the light source to the light output port. The lighting
device further includes: a filter plate having a size similar to a
size of the plurality of segments of the heat dissipating base; and
a second wheel carrying the filter plate; wherein the control unit
controls a movement of second wheel to move the filter plate in and
out of an optical path between the heat dissipating base and the
light guiding device. The heat dissipating base of the wavelength
conversion wheel assembly includes at least one segment that
carries a wavelength conversion material, the heat dissipating base
further comprising a wavelength selection filter film or filter
plate disposed in the at least one segment on a side facing the
excitation light.
[0018] More specifically, the lighting device may further include a
second focusing lens for focusing the excitation light onto the
wavelength conversion material on the heat dissipating base. It may
further include a second collimating lens disposed between the heat
dissipating base and the focusing lens for collimating the light
from the light source into a near parallel light to be focused by
the focusing lens. It may further include an integral lens set
disposed between the second collimating lens and the focusing lens.
It may further include a pattern wheel carrying pattern plates
aligned with the light output port.
[0019] In another aspect, the present invention provides a color
tuning method for a lighting device, wherein the lighting device
comprises a light source, a light output port, and a light guiding
device for guiding the light from the light source to the output
port, wherein the light source includes an excitation light source
for providing an excitation light, the method including:
[0020] Providing a moving unit, wherein the moving unit includes
the wavelength conversion wheel assembly of any one of claims 1-10,
wherein the heat dissipating base faces the excitation light and is
partially illuminated by the excitation light, wherein an area of
illumination is no greater than an area of any one of the
segments;
[0021] Operating a control unit to control the wavelength
conversion wheel assembly, wherein the wavelength conversion wheel
assembly moves so that a selected one of the plurality of segments
is disposed in an illumination path of the excitation light;
and
[0022] Generating an output light of a selected color, wherein the
color of the output light is determined by the excitation light
source and the selected segment or the wavelength conversion
material carried by the selected segment.
[0023] In the above method, the excitation light source includes an
array of a plurality of light emitting diodes (LED) and an array of
a plurality of collimating lenses, each collimating lens being
aligned with an LED to collimate a light emitted by the LED into
near parallel light. The LEDs are blue LEDs.
[0024] In the above method, the heat dissipating base is made of a
transparent material or have a plurality of through holes in which
the segments are disposed, and the method further includes:
providing a filter plate or filter film on or near the heat
dissipating base on a side facing the light guiding device, wherein
the filter plate or filter film is disposed in an optical path
between the heat dissipating base and the light guiding device for
selectively transmitting light of a predetermined wavelength range
or predetermined output angle range. The method further includes:
coating or disposing a wavelength selection filter film or filter
plate on the heat dissipating base on a side facing the excitation
light for reflecting the converted light.
[0025] In the above method, the operating step includes operating
the control unit at predetermined times or intermittently according
to a predetermined color changing pattern to select the segments or
filter plates. The method further includes: the control unit
controlling the excitation light and the moving unit in a
synchronized manner. The control unit includes a stepping motor for
driving the wavelength conversion wheel assembly via gears.
[0026] Embodiments of the present invention provide a stage
lighting device and color tuning method that are easy to implement
and easy to control, and can be achieved at low cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 illustrates the structure of a conventional stage
lighting device having a light combiner to provide output light of
various colors.
[0028] FIG. 2 illustrates a lighting device according to an
embodiment of the present invention.
[0029] FIG. 3 illustrates a wavelength conversion wheel assembly
according to an embodiment of the present invention. FIG. 3a is a
side view and FIG. 3b is a front view.
[0030] FIG. 4 illustrates a wavelength conversion wheel assembly
according to an improved embodiment of the present invention,
viewed in the direction indicated by the arrows in FIG. 3b.
[0031] FIG. 5 illustrates a wavelength conversion wheel assembly
according to an alternative embodiment of the present
invention.
[0032] FIG. 6 illustrates a lighting device according to a second
embodiment of the present invention.
[0033] The reference symbols in the figures represent: 1--LED
array, 2--collimating lens array, 3--second focusing lens,
4--moving unit/wavelength conversion wheel assembly, 5--second
collimating lens, 6--integral lens, 7--focusing lens, 8--light
output port, 40--heat dissipating base, 41--areas carrying
wavelength conversion materials, 42--areas free of wavelength
conversion materials, 43--rotating shaft, 44--gear, 45--filter,
46--wavelength conversion material, 47--heat conducting plate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] Preferred embodiments of the present invention are described
below with reference to the drawings.
[0035] Atypical lighting device includes a light source, a light
output port where a pattern wheel or pattern plates may be
disposed, and a light guiding device for guiding the light from the
light source to the output port. As shown in FIG. 2, the light
guiding device may use a focusing lens 7, which focuses the light
from the light source to the output port 8. The light guiding
device may also use a tapered light guiding rod 7', as shown in
FIG. 6. The tapered light guiding rod may be a solid glass rod, or
a hollow rod coated with high reflecting film or covered with
reflective plates on the inner surface, to generate a uniform light
spot with a relatively short optical path. In this embodiment, the
light source uses a wavelength conversion scheme, and includes an
excitation light source for generating an excitation light, and a
moving unit. As shown in FIG. 2, the excitation light source may be
a solid state light source, in particular, an array of multiple
solid state light sources (such as but not limited to LED array 1),
which can reduce cost and improve output power and brightness of
the source. FIG. 2 also shows an array of multiple collimating
lenses 2, each collimating lens being aligned with one LED to
collimate the large angle light emitted by each LED into near
parallel light with a small divergence angle. This improves the
light utilization efficiency. A key component of this embodiment is
the moving unit, which includes a wavelength conversion wheel
assembly 4 shown in FIG. 2.
[0036] FIG. 3 illustrates the assembly 4 in more detail. The
assembly includes a heat dissipating base 40, shown in the front
view in FIG. 3b, which defines a number of segments for
respectively carrying various wavelength conversion materials (e.g.
segments 41) or carrying no wavelength conversion material (e.g.
segment 42). It also includes a solid or hollow rotation shaft 43.
The heat dissipating base is controlled to rotate intermittently or
rotate to predefined angles around the rotation shaft. The number
of segments is determined by the stage lighting requirements, and
the number is typically three or more. For easy control, the
segments should have similar or identical sizes, and their shapes
may be circular (to match the shape of commonly used pattern
plates), but are not limited thereto. The segments are distributed
in a circular manner on the heat dissipating base. The wavelength
conversion materials include phosphor, dye or quantum dots, which
absorb the excitation light and emit converted light of various
wavelengths different from the excitation wavelength. The
wavelength conversion materials may be applied to the segments by
coating, filling in, adhering, etc. The different wavelength
conversion materials in the different segments may be different
types of wavelength conversion materials which generate converted
light of different colors under the same excitation light; or they
may be the same wavelength conversion materials but having
different concentrations or different layer thicknesses, or
different mixtures of various amounts of two or more wavelength
conversion materials, so that they generate lights of different
color saturation or different color temperature under the same
excitation light. To generate a light having the same color as the
excitation light, a segment may be a transparent or reflective
segment that carries no wavelength conversion material.
[0037] The heat dissipating base 40 may be formed of a transparent
material, for example but not limited to two highly heat conductive
glass plates clamped together, where the wavelength conversion
materials are sandwiched between the two glass plates. The side
view of FIG. 3a shows the presence of a filter film or filter plate
45, which is coated on or carried by the heat dissipating base 40,
and aligned with at least one segment of the base. The heat
dissipating base 40 may also be made of a nontransparent material,
as shown in the side cross-sectional view of FIG. 4, where the heat
dissipating base 40 has a number of heat dissipating plates with
through holes, and each segment is disposed in a through hole. The
wavelength conversion materials 46 are carried by transparent heat
conducting plates 47 (such as heat conducting glass) nested in the
through holes. Filter films or filter plates 45 may be additionally
disposed in the through holes as shown in the figure. The heat
dissipating plates may be provided with multiple blades (not shown)
to increase the heat dissipating area. Based on the following
relationship regarding the wavelength conversion material,
E.sub.output=E.sub.input*.eta..sub.oc*.eta..sub.stokes
where E.sub.output is the energy of the converted light,
E.sub.input is the energy of the input excitation light,
.eta..sub.oc is the quantum efficiency (typically less than 1), and
.eta..sub.stokes is the Stokes shift efficiency, i.e. the
conversion efficiency of converting from one wavelength to another
wavelength. When a blue light centered at 460 nm is converted to a
light centered at 530 nm, .eta..sub.stokes=460/530=0.87. The longer
the wavelength, the lower the conversion efficiency, and the lost
light energy is converted to heat. Better heat conductivity of the
heat dissipating base 40 and the heat conducting plates 47 helps
increase the light conversion efficiency of the wavelength
conversion material 46, and helps avoid burn out of the phosphor
due to heat accumulation. Highly heat conductive transparent
materials include but are not limited to sapphire.
[0038] The heat dissipating base 40 in the above two embodiments
are suitable for transmission type optical arrangements. For a more
compact design, reflection type optical arrangements may be used,
where the heat dissipating base 40 is additionally provided with a
reflective coating to reflect the converted light and the
unabsorbed excitation light.
[0039] The wavelength conversion wheel assemblies shown in FIG. 3
and FIG. 4 have a generally plate shape or planar shape. As shown
in FIG. 5, the assembly may also have the shape of a cylindrical
surface, where the various segments 41, 42 are disposed on the
cylindrical surface of the heat dissipating base 40. The
cylindrical surface may be made of transparent or non transparent
materials.
[0040] The rotation shaft 43 in FIGS. 3-5 can be used to
mechanically support the wavelength conversion wheel assembly 4.
The gear 44 disposed around the rotation shaft 43 is used to
control the rotation of the wheel assembly to select the segment
being illuminated by the excitation light. As an alternative, as
will be recognized by those skilled in the art, the gear 44 may be
disposed around the outer edge of the heat dissipating base 40, and
the rotation shaft 43 may be replaced by other suitable components
(for example but not limited to a bolt) to mount the heat
dissipating base 40. Regardless of the specific mechanical
structure, the heat dissipating base 40 has a rotation axis, and
any suitable implementations are within the scope of this
invention.
[0041] When the assembly 4 is used in a lighting device according
to an embodiment of the present invention, as shown in FIG. 2, the
heat dissipating base 40 faces the excitation light and a segment
of it is illuminated. The area of illumination is equal to or
smaller than the area of any of the segments. The lighting device
additionally includes a control unit (not shown in the drawings)
for controlling the rotation of the wavelength conversion wheel
assembly so that a selected one of the segments of the heat
dissipating base 40 is in the optical path of the excitation light
to generate desired output light.
[0042] In a preferred embodiment, to increase conversion efficiency
of the phosphor material, the lighting device further includes a
second focusing lens 3 which focuses the near parallel light having
a relatively large area onto a smaller area of the heat dissipating
base 40 where wavelength conversion materials are carried. This
reduces the etendue of the optical system. The second focusing lens
3 may be made of a glass or plastic material and may be a spherical
lens or an aspheric lens.
[0043] Considering that the converted light from the phosphor
material has a Lambertian distribution, i.e., the converted light
is emitted by the phosphor material at a 180 degree full width
distribution, a second collimating lens 5 may be disposed between
the heat dissipating base 40 and the focusing lens 7. The light
collection angle of the second collimating lens 5 is preferably
greater than 120 degrees in full width, to collimate the large
angle light emitted by the phosphor and direct it to the focusing
lens 7. An integral lens set 6 is disposed between the second
collimating lens 5 and the focusing lens 7 to make the output light
spot more uniform in brightness and/or color. A disadvantage of
using the integral lens set 6 is that it increases the length of
the optical system. These optical components are well known in
relevant art and are not described in detail here. It should be
noted that except for the moving unit 4, other components of the
system shown in FIG. 2 may be replaced by alternative components.
For example, in lieu of the focusing lens 7 and the second
collimating lens 5, the light guiding device may use an optical
fiber having a suitably large aperture. If a light collecting
assembly is used near the heat dissipating base 40 to reduce the
size of the output light, an optical fiber having a smaller
aperture may be used for this purpose. In addition, if the light
source does not need to be controlled in real time, the excitation
light source may use conventional monochromatic light sources such
as UV light in lieu of solid state light sources such as LED or
laser diode.
[0044] If the wavelength conversion wheel assembly 4 is not
provided with a filter plate of filter film on the surface facing
the light guiding device, then the lighting device may be provided
with an additional wheel carrying a filter plate having a similar
size as the segments of the wavelength conversion wheel assembly.
The control unit controls the movement of this additional wheel to
move the filter plate in and out of the optical path between the
heat dissipating base 40 and the light guiding device.
[0045] Using the above described lighting device, a method
according to an embodiment of the present invention for tuning the
color of the output light is summarized below:
[0046] Providing a moving unit, including the wavelength conversion
wheel assembly 4;
[0047] Providing or operating a control unit to control the moving
unit, wherein the wavelength conversion wheel assembly moves such
that a selected segment of the wavelength conversion wheel assembly
is disposed in the illumination path of the excitation light;
and
[0048] Generating an output light of a selected color, wherein the
color of the output light is jointly determined by the excitation
light source and the selected segment or the wavelength conversion
material carried by the selected segment.
[0049] More specifically, the method includes the following steps,
using as an example a blue LED array as the excitation light
source, a phosphor as the wavelength conversion material, and
transmission type segments on the wavelength conversion wheel
assembly. When a segment carrying a yellow phosphor is controlled
to enter the optical path of the excitation light, the output light
is white as a result of the blue excitation light mixing with the
yellow converted light. When the heat dissipating base uses a
transparent material, or the segments are nested in through holes
of the heat dissipating base, the method may further include a step
of providing a filter plate or filter film on or adjacent the heat
dissipating base on the side facing the light guiding device, for
selectively transmitting light of a predetermined wavelength range
or predetermined output angle range. For example, a blue-blocking
filter may be provided between the heat dissipating base and the
light guiding device to filter out blue light. When such a filter
is provided, if a yellow phosphor segment of the heat dissipating
base is in the optical path, then the output light will be a yellow
light; if a red phosphor segment is in the optical path, then the
output light will be a red light; and if a green phosphor segment
is in the optical path, then the output light will be a green
light; etc. Likewise, when the excitation light source is a UV LED
and a UV-blocking filter is used, similar results can be obtained.
When the filter plate or filter film is one that can selectively
transmit light of a certain range of output angles, the divergence
angle of the output light can be improved, and a low divergence
output light can be obtained, which may eliminate the need for the
second collimating lens 5. Further, because a part of the converted
light generated by the wavelength conversion wheel assembly will
travel toward the excitation light source, to effectively output
the converted light, a wavelength selection filter film or filter
plate may be provided on the heat dissipating base 40 or the heat
conducting plate 47 on the side facing the excitation light. The
wavelength selection filter reflects the converted light and
transmits the excitation light, thereby effectively outputting the
converted light, increasing the utilization rate of the converted
light and the brightness of the lighting device. Because the
wavelength range of the excitation light is shorter than that of
the converted light, the wavelength selection filter may be a low
pass optical filter which transmits shorter wavelength light and
reflects longer wavelength light.
[0050] The method according to embodiment of the present invention
further includes a step of using a control unit for controlling the
excitation light source and the moving unit in a synchronized
manner. For example, when the control unit controls the wavelength
conversion wheel assembly 4 to move, it simultaneously cuts off the
drive power to the excitation light source; when the wavelength
conversion wheel assembly stops moving, the control unit turns on
the drive power to the excitation light source. This generates a
converted light having a discontinuous color changing effect.
[0051] To generate output light with repeating or programmed color
change, a manual or predetermined color changing pattern can be
provided; thus, by operating the control units at predetermined
times or intermittently, the wheel segments or filters can be
selected in a desired manner. The control unit may include a
stepping motor to drive a gear set to move the wavelength
conversion wheel assembly. Digital technology may be used to
control the above operations of the control unit; such control can
be readily implemented by those skilled in the relevant art and are
not described in detail here.
[0052] In the device and method according to embodiments of the
present invention, in addition to using the various segments of the
wavelength conversion wheel assembly to change the color or color
temperature of the output light, different excitation light sources
may be used in combination with the different segments to adjust
the color or color temperature of the output light. For example, in
the above described examples, the excitation light source is a
monochromatic source; but the excitation light source may also
include LEDs or LED arrays that emit lights of two or more colors.
For example, a small number of red LEDs may be added to a blue LED
array; when a yellow phosphor is used, then the output white light
will have a reddish color. Alternatively, to obtain a more uniform
light distribution, the red LEDs may be formed into a separate
array, as shown in FIG. 6, and the red light and blue light may be
combined by a light combining unit 3' into the excitation light
beam. Details of other examples are omitted.
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